To reduce an amount of leakage of a working fluid flowing from a high-pressure side to a low-pressure side, a shaft sealing apparatus is installed around a rotor in a rotating machine such as a gas turbine or a steam turbine. As an example of the shaft sealing apparatus, for example, the shaft sealing apparatus disclosed in Patent Document 1 below is known.
Such a shaft sealing apparatus is equipped with a housing installed on a stator, and a seal body made up of numerous thin seal pieces.
The seal body is configured so that the numerous thin seal pieces are stacked apart from each other at minute intervals with a thickness direction of each thin seal piece directed in a circumferential direction of a rotor. Each thin seal piece is slantingly disposed so that a radial inner end (front end) thereof is located at a position closer to a rotating-direction front side of the rotor than a radial outer end (rear end) thereof. The thin seal pieces are configured so that the rear ends thereof are connected to one another, and so that the front ends thereof are free ends.
In the shaft sealing apparatus schematically configured in this way, when the rotor stands still, the front end of each thin seal piece is in contact with the rotor. In contrast, when the rotor rotates, the front end of each thin seal piece is raised from an outer circumference of the rotor and comes out of contact with the rotor due to a dynamic pressure effect caused by the rotation of the rotor. For this reason, in the shaft sealing apparatus, the wear of each thin seal piece is suppressed, which enables a seal service life to be increased.
On the other hand, particularly, when the rotating machine is started, pipe scale (rust, etc.) may flow from an upstream side into the seal body. This causes the pipe scale to be in a clearance between the thin seal pieces and between the seal body and a surface of the rotor. Thus, there is a possibility of the sealing performance being reduced, or of the durability being reduced due to the occurrence of wear.
As a means of avoiding this phenomenon, a biasing means of biasing a housing toward a radial outer side of the rotor is provided. Thereby, an automatic clearance adjusting function of moving the seal body toward a radial outer side with a biasing force at the time of startup/stop, and of moving the seal body toward a radial inner side with seal differential pressure at the time of rated operation is known.